undocumented Query Params - missing hint in documentation or successful just by chance?

Hi,

in the api scenario "list contacts" I was missing the query parameter for the field integration_code (which we plan to use as a foreign key to our pk in our ERP system - I hope this is the correct usage of this field).

I just tried to add this to the API call: ?integration_code=00268686 and it worked!

Is this a stable reliable functionality or just working currently by chance?

Maybe it would be usefull to add a hint in the api reference, which fields (maybe any?) can be used for filtering lists. If it is already, I didn't realize it and will apologize for it.

Best Regads,

Thomas